Choose olives that are intact, wash them, put them to soak in cold water with a handful of salt for 10-14 days; change the water every day. After this period of time they will have lost the majority of their bitterness. Strain them and put them in glass jars, in brine made as follows: for every kg of olives, 70 g of salt dissolved in 1 litre of water. Close each jar – the olives must be well covered by the brine – with a screw top and keep them in a cool place, away from the light. After 7-10 days (but taste them, and if they still seem bitter, extend the “treatment” for another 2 or 3 days) they will be ready to eat. If they stay well covered, in a cool place or the fridge, they keep for several weeks.